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Comment: Re:A Progression of Complaints (Score 2) 190

by richard.cs (#47569427) Attached to: UK To Allow Driverless Cars By January

What do you think happens when you step on the gas pedal? Do you think it's still physically pulling some cable that opens flapper valves, allowing more fuel to flow into a carburetor?

I haven't worked on anything newer than about 10 years old but every fuel-injected petrol engine I've played with has had a mechanical butterfly valve operated by the pedal. The fancy electronics then measures mass flow rate (which is a function of throttle plate position, air temperature, air filter condition, engine rpm, etc) and injects the right amount of fuel. It's not *that* different from a mechanical carburettor except that carburettors measure volumetric flow and have to be tweaked for summer/winter to account for the different air inlet temperature

What about that transmission? Unless you drive manual, you're not actually moving gears around with that lever. You're sending a signal to a computer "Put it in drive" which was also designed by a programmer.

Where I'm from (UK) nearly everyone has a manual transmission :-)

Comment: Re:FUD filled.... (Score 1) 212

I doubt natural gas gets from point a to point b by magic.

Natural gas is generally pumped around by turbines burning natural gas, it's cheaper but also happens to be immune to electrical problems. Failure of controls cause valves to stick in their last commanded position though so expect at least some problems with pressure fluctuations, etc.

Comment: Re:New possibilities (Score 1) 333

by richard.cs (#45370163) Attached to: Solid Concepts Manufactures First 3D-Printed Metal Pistol

Even if the machine itself could handle it (i.e., had multiple material-handling streams), you would have a tough time getting the dissimilar metals to properly fuse

I find the idea of changing materials part-way through a piece interesting, you might not be able to fuse them but I'm imagining something similar to a dovetail joint, printed in place and utterly permanent. Essentially just mechanically interlocking the different materials during printing.

Comment: Re:spiral arms? (Score 4, Interesting) 199

by richard.cs (#44913591) Attached to: Linking Mass Extinctions To the Sun's Journey In the Milky Way

Do the spiral arms move w/respect to all the stars like some sorta density wave?

That's exactly what the spiral arms are, they can't be the same stars orbiting together in that shape as that would imply a rigid body rotation. The situation where everything moves around together as if it were nailed to a rigid cosmic disc doesn't work because the orbit time of the stars at the centre of the galaxy is less than that of the stars at the edge. This is a consequence of the orbital physics, it's essentially the only way the forces can balance.

So, the stars in the centre whiz around quickly (in cosmological time anyway) whilst the ones at the edge take forever. The spirals are simply areas of higher star density but they are not the same stars all the time. This region does rotate but more slowly than the stars contained within it. So, why are there areas of increased star density? No-one's entirely sure but it seems likely that these are actually regions with higher rates of star formation, with many young, short-lived blue stars.

Comment: Re:Disintegration (Score 1) 272

by richard.cs (#44847749) Attached to: It Takes 2.99 Gigajoules To Vaporize a Human Body

80kg of water is about 136m^3 (4,800 cubic feet) of steam, so you'd better make sure there's a window open cos that's the volume of a cube with sides of nearly 17ft.

80kg of water is about 0.8m^3

80 kg of water is 0.08 m^3 (1 litre of water being a cube 0.1 meters each side and of mass 1kg), if you turn it into steam it expands by about 1700 so assuming atmospheric pressure gives 0.08*1700= 136 m^3 of steam as the OP stated.

Comment: Re:It's news worthy but isn't at the same time ... (Score 1) 180

by richard.cs (#44398285) Attached to: GPS Spoofing With $3000 Worth of Equipment and a Laptop

This is well known to be possible, has been done for years, and you can buy commercial test equipment that sends spoof GPS signals (for testing GPS receivers obviously). More importantly there's another simpler way that cannot be dealt with by signing - just relay GPS signals from elsewhere.

If you capture GPS data at a point in space and retransmit the whole lot with enough power that the receiver sees only your signals then the receiver sees all the same phase relationships that put it in the location where you captured the data. It has no way of knowing it's been delayed by a few microseconds and signed GPS signals would look perfect. The only way around that is to compare it with inertial navigation, loran, etc or perhaps to have a very accurate clock on board to try and spot the extra delay.

Comment: Re:Nope, can't make a gun-type with Pu (Score 1) 192

by richard.cs (#44353135) Attached to: Interactive Nukemap Now In 3D

You can make a gun-type bomb with impure plutonium, what you can't do is make one short enough to deliver in a missile or a plane. Built diagonally on the 100th floor of an office building or more feasibly at ground level in a dockside warehouse however....

You "just" need to increase the assembly velocity, and there are ways of doing that which are simpler than building an implosion device. And as you point out a fizzle is still a significant yield, and much dirtier.

Give a final year physics student a mechanical workshop and the plutonium, all they'd need is the funding.

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